1+ '''
2+ Created on Aug 9, 2017
3+
4+ @author: Aditya
5+
6+ This file gives the demonstration of 4 basic and most important function of database
7+ CRUD :: Create - Retrieve - Update - Delete
8+ '''
9+ 10+ import sqlite3 # import python database lib
11+ 12+ def insert (db , row ): # function to insert rows in database
13+ # db - database object
14+ # row - row to be inserted in the database
15+ db .execute ('insert into test (t1, i1) values (?, ?)' , (row ['t1' ], row ['i1' ])) # insert row into the database
16+ db .commit ()
17+ 18+ 19+ def display_rows (db ): # function to display rows from database
20+ # db - database object
21+ cursor = db .execute ('select * from test order by t1' )
22+ for row in cursor :
23+ print ('{}:{}' .format (row ['t1' ],row ['i1' ]))
24+ 25+ def retrieve_row (db , key ): # to retrieve data from database
26+ cursor = db .execute ('select * from test where t1 = ?' , (key ,)) # note that argument is passed as single element tuple
27+ return cursor .fetchone () # fetch one data from database
28+ 29+ def update_row (db , row ): # to update row in database
30+ db .execute ('update test set i1 = ? where t1 = ?' , (row ['i1' ], row ['t1' ]))
31+ db .commit ()
32+ 33+ def delete_row (db , key ): # to delete row from database
34+ db .execute ('delete from test where t1 = ?' , (key ,))
35+ db .commit ()
36+ 37+ def main ():
38+ print ('Note: Call commit() on database after doing any change in it.' )
39+ db = sqlite3 .connect ('TestDB.db' ) # creating and connecting to test database
40+ db .row_factory = sqlite3 .Row
41+ 42+ print ('Create a table named \' test\' in the database' )
43+ db .execute ('drop table if exists test' )
44+ db .execute ('create table test (t1 text, i1 int)' )
45+ 46+ print ('Create Rows' )
47+ insert (db , dict (t1 = 'one' , i1 = '1' )) # insert table rows in database in dictionary form
48+ insert (db , dict (t1 = 'two' , i1 = '2' ))
49+ insert (db , dict (t1 = 'three' , i1 = '3' ))
50+ insert (db , dict (t1 = 'four' , i1 = '4' ))
51+ insert (db , dict (t1 = 'five' , i1 = '5' ))
52+ insert (db , dict (t1 = 'six' , i1 = '6' ))
53+ insert (db , dict (t1 = 'seven' , i1 = '7' ))
54+ display_rows (db )
55+ 56+ print ('Retrieve data from database' )
57+ print (dict (retrieve_row (db , 'one' )), dict (retrieve_row (db , 'two' )))
58+ 59+ print ('Update row in database' )
60+ update_row (db , dict (t1 = 'one' , i1 = 101 ))
61+ update_row (db , dict (t1 = 'two' , i1 = 102 ))
62+ display_rows (db )
63+ 64+ print ('Delete rows' )
65+ delete_row (db , 'one' )
66+ delete_row (db , 'two' )
67+ display_rows (db )
68+ 69+ if __name__ == '__main__' :main ()
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